'A wind of change': changes in position and intensity of the southern hemisphere westerlies during oxygen isotope stages 3, 2 and 1

This thesis investigates past climate change in southern part of the world, and more particularly the mid-latitudes of the Southern Hemisphere using lake sediments. Three different locations within these latitudes were selected for this investigation: 1) Lac d'Armor, a medium-sized lake on the Kerguelen Archipelago (49°S), 2) four large lakes (Lago Villarrica, Lago Calafquén, Lago Panguipulli and Lago Riñihue) in the Chilean Lake District (39-40°S) and 3) Laguna Parrillar, a medium-sized lake in Southern, Chilean Patagonia (53°S). The main focus of this research is to better understand the behaviour of this Southern Westerly wind system during the last 45000 years of the Earth's history. Two type of techniques were used to study these sediments. First of all a seismic survey was performed, with this technique an acoustic image is created of the entire lake basin infill is created. This allows a quasi three dimensional reconstruction of the sediment accumulation in the basin. Consequently the evolutionary history of this basin can be reconstructed. The resolution of this technique is, however, rather low (e.g. millenial time scale). Therefore, short term variations will not be represented in such a record. To bypass this limitation, sediment cores can be taken of the same lake sediment . A sediment core record will not span the same large time span as a seismic record, nor will it allow a three dimensional reconstruction, but it will allow the reconstruction of climatic variations on a high resolution time scale (centennial to decadal scale). Combining both techniques the climatic history of a region can be unraveled in its every aspect. All of these lake sediment archives record changes in the intensity of the Southern Hemisphere Westerlies. When absolute ages are available these changes seem to be rather synchronous at both 39°S and 53°S, therefore not really indicating clear shifts of the Southern Westerlies. There is, however, a slight asynchronous behaviour during the last 1000 years, a period during which the influence of the El Niño Southern Oscillation is strong South Central Chile